小编use*_*264的帖子

为什么在函数中执行一组命令:

def main():
    [do stuff]
    return something
print(main())

在python中运行速度比在顶层执行命令1.5x要3x快得多:

[do stuff]
print(something)

我最近更新了我的应用并尝试运行它,并得到以下关于"地址已在使用中"的错误.这是什么意思,我该如何解决？

Traceback (most recent call last):
  File "/home/ubuntu/workspace/app.py", line 11, in <module>
    app.run(host = os.getenv('IP', '0.0.0.0'), port=int(os.getenv('PORT',8080)))
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 772, in run
    run_simple(host, port, self, **options)
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 687, in run_simple
    inner()
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 653, in inner
    fd=fd).serve_forever()
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 557, in make_server
    passthrough_errors, ssl_context, fd=fd)
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 467, in __init__
    HTTPServer.__init__(self, (host, int(port)), handler)
  File "/usr/lib/python2.7/SocketServer.py", line 419, in __init__
    self.server_bind()
  File "/usr/lib/python2.7/BaseHTTPServer.py", line 108, in server_bind
    SocketServer.TCPServer.server_bind(self)
  File "/usr/lib/python2.7/SocketServer.py", line 430, in server_bind …

我刚开始学习 Haskell，但我遇到了困难，因为错误消息非常神秘。特别是，当我运行这个应该打印字符串排列数的代码时，我不理解错误消息，

import Data.List

main::IO()
main = do
        str <- getLine
        print putStrLn $ length $ nub $ permutations str

我得到的错误信息是

但是，当我在 REPL 中运行它时，我没有收到这样的错误：